1. Field of the Invention
The present invention relates to a transfer method of a colored image in a full-color copying apparatus or the like employing therein an intermediate transfer medium.
2. Description of the Prior Art
Conventionally, in a full-color copying apparatus employing an intermediate transfer medium such as an intermediate transfer belt, toner images in three primary colors (yellow, magenta and cyan) are initially independently formed on a photoconductor belt. The toner images are overlapped one upon another on the intermediate transfer belt, and a resultant toner image is transferred onto a copy paper sheet.
In the conventional full-color copying apparatus, the voltage applied to a transfer roller is kept constant. Accordingly, in view of the transfer efficiency for example, it is necessary to make the size of the intermediate transfer belt longer than the maximum size of copy paper sheets usable in the apparatus. It is also necessary to make the distance between the transfer roller and a fixing device longer than the maximum size of the copy paper sheets. In other words, the size of the apparatus is restricted by the maximum size of the copy paper sheets. This is disadvantageous because it is difficult to form the apparatus to a compact size.